Apparatus and method for extending the length of a vent pipe above the elevation of a building roof

ABSTRACT

Apparatus and a method for extending the length of a vent pipe for a predetermined distance above the elevation of a building roof includes an elongated extension pipe connectable with the vent pipe, a flashing attachable to the roof while fitted as a sleeve over the extension pipe, and a vent cap fittable over the flashing and the extension pipe. The vent cap includes an opening for venting to external atmosphere gases received by the extension pipe from the vent pipe. The extension pipe and the vent cap are sized so as to maintain a venting pressure in the extension pipe not greater than the venting pressure in the extension pipe.

BACKGROUND TO THE INVENTION

[0001] The present invention relates to vent pipes for building roofs and to methods for extending the length of such pipes.

[0002] Many existing flat roof buildings are simply flat and lack a suitably effective roof drainage system. Depending on the size of the roof, hundreds and sometimes thousands of gallons of water can collect, and this may lead to significant structural damage. When it comes time to upgrade or to repair the roof, the water must be removed and this can be a very difficult job. To avoid reoccurrence of the problem, it is not uncommon for the roof to be redesigned with an effective drainage system.

[0003] When an existing roof is redesigned, one technique that has evolved is to build a new roof atop the old roof. The old flat roof is built up higher on its perimeter with a new roof that slopes to a slight but sufficient degree towards one or more appropriate drains. Once installed, water cannot pond on the roof and the risk that water will produce a significant amount of weight on the roof is eliminated.

[0004] However, as representationally illustrated in FIG. 7, the raising of an old roof can lead to other problems. FIG. 7 depicts part of an old building roof 100, an existing cylindrical vent pipe 150, a new building roof 200 constructed atop the old roof, and insulation 250 carried between the old roof and the new roof. Although imperceptible in the drawing, care will have been taken to ensure that new roof 200 has sloping characteristics (lacking in old roof 100) to ensure adequate drainage.

[0005] With the addition of a new roof 200, but not in all cases, a decision may also be made to add a layer of insulation such as insulation 250. Styrofoam insulation, tapered to provide the desired sloping characteristics of the new roof, may be used to provide insular qualities.

[0006] Typically, the purpose of a vent pipe such as vent pipe 150 is to vent gases* from one or more areas of a building (e.g. the building plumbing system, a kitchen, a shower, etc.). Several such vent pipes may be present in any given building. As is plainly evident from FIG. 7, an immediate problem is that vent pipe 150 does not extend above the elevation of new roof 200. Other vent pipes (not shown) similarly may not extend above the elevation of new roof 200 or, if they do, not by a sufficient amount.

[0007] Parenthetically, it may be noted that existing plumbing vent pipes typically may be extended approximately 11 inches above an existing flat roof deck. Depending on the overall size of the existing roof, a new sloped roof such as roof 200, including a layer of insulation such as insulation 250 may, in some cases, add more 16 inches to the height of the existing roof.

[0008] Accordingly, pipes such as vent pipe 150 have to be extended. Typically, this has been done by inserting an extension pipe of desired length within the existing vent pipe. A flashing, sleeved over the extension pipe and attached to the new roof, is added in a conventional manner, and a vent cap is placed over the extension pipe and flashing in a conventional manner. However, this convention has been found to lead to further problems. It has been realized that moisture from venting gases may pass between the extension pipe and the flashing with consequent damage to the building structure, and that this problem is not resolved by conventional designs.

[0009] Thus there is a need for improved apparatus and a method to extend the length of existing vent pipes which discourages or at least does not encourage the passage of moisture laden gases between an extension pipe and its flashing.

[0010] It is an object of the present invention to provide new and improved apparatus for extending the length of an existing vent pipe for a predetermined distance above the elevation of a building roof - more specifically, apparatus that serves to obstruct or discourage venting gases from passing between an extension pipe and related flashing.

[0011] Further, it is an object of the present invention to provide a new and improved method of extending the length of an existing vent pipe in an building above the elevation of a new roof added atop the old roof of the building.

[0012] In meeting the foregoing objects, it is also an object of the present invention to provide apparatus for extending the length of a vent pipe which is easy to manufacture, and which is easy to assemble and install on a roof, including a new roof which is constructed atop an existing roof.

SUMMARY OF THE INVENTION

[0013] In a broad aspect of the present invention, there is provided apparatus for extending the length of an existing vent pipe for a predetermined distance above the elevation of a building roof, the apparatus comprising

[0014] an elongated extension pipe connectable with the vent pipe to receive gases flowing upwardly from the vent pipe;

[0015] a flashing attachable to the roof while fitted as a sleeve over the extension pipe; and,

[0016] a vent cap fittable over the flashing and the extension pipe to shield the annular region between the flashing and the extension pipe from external precipitation.

[0017] The vent cap includes an opening for venting to external atmosphere gases received by the extension pipe from the vent pipe. Further, the extension pipe and the vent cap are sized so as to maintain a venting pressure in the extension pipe not greater than the venting pressure in the extension pipe.

[0018] The present invention recognizes that the problem noted above can be attributed to back pressures caused by the reduction of flow areas. Since the region within the extension pipe will be a region of reduced pressure compared to the pressure within the existing vent pipe, the present invention serves to avoid any undue choking effect at the outlet as provided by the opening in the vent cap. This is advantageous because when gases are choked at the vent cap outlet, the higher choke pressure may force at least some of the gases into the annular space between the extension pipe and the flashing. Since this space is a sleeve space it typically may have a small width. Nevertheless, it exists. In the absence of glues or other sealing mechanisms which are desirable to avoid (and which in any event may deteriorate over time), the space provides a path where some moisture carried by venting gases may find its way with eventual damage to the building structure. This risk can be higher when the venting gases are moisture laden and have a relatively high temperature. At higher temperatures components that are otherwise relatively tight fitting may expand and loosen.

[0019] In a preferred embodiment, the extension pipe is characterized by a lower end having a cylindrical outside diameter sized to fit snugly within an inside diameter of the vent pipe, and an elongated tubular portion extending upwardly from the lower end. The tubular portion has an inside diameter greater than the inside diameter of the vent pipe. The flashing comprises a base attachable to the roof and a centrally positioned tubular portion extending upwardly from the base. The tubular portion of the flashing is characterized by an inside diameter sized to fit as a sleeve over the extension pipe. The base of the flashing includes a centrally aligned opening having a diameter corresponding to the inside diameter of the tubular portion of the flashing. The opening extends through the base for permitting the flashing to be lowered as a sleeve over the extension pipe. The vent cap comprises an inner wall and an outer wall with an annular space defined between the walls, the annular space having a closed top and an open bottom. The inner wall defines a centrally aligned opening extending lengthwise through the cap. Also, the inner wall has an outside diameter sized to slidingly fit within the inside diameter of the extension pipe. The outer wall has an inside diameter sized to slidingly receive the outside diameter of the tubular portion of the flashing.

[0020] In another aspect of the present invention, where a new building roof is constructed atop an old building roof, and where an existing vent pipe extending above the old roof is of insufficient length in relation to the new roof, there is provided a method of extending the length of the existing vent pipe above the elevation of the new roof, the method comprising:

[0021] connecting an upwardly extending, elongated extension pipe with the vent pipe to receive gases flowing upwardly from the vent pipe, the extension pipe having sufficient length to extend from the vent pipe to a desired distance above the new roof;

[0022] fitting a flashing as a sleeve over the extension pipe;

[0023] attaching the flashing to the new roof when so fitted; and,

[0024] fitting a vent cap over the flashing and the extension pipe to shield the annular region between the flashing and the extension from external precipitation, the vent cap including an opening for venting to external atmosphere gases received by the extension pipe from the vent pipe.

[0025] The extension pipe and the vent cap are sized to maintain a venting pressure in the extension pipe not greater than the venting pressure in the extension pipe.

[0026] The foregoing and other features and advantages of the present invention will now be described with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is an exploded view of component parts of vent pipe extension apparatus in accordance with the present invention.

[0028]FIG. 2 is an enlarged section elevation view of the coupler shown in FIG. 1.

[0029]FIG. 3 is an enlarged section elevation view of the extension pipe shown in FIG. 1.

[0030]FIG. 4 is an enlarged section elevation view of the flashing shown in FIG. 1

[0031]FIG. 5 is an enlarged section elevation view of the vent cap shown in FIG. 1.

[0032]FIG. 6 is an enlarged section elevation view of the apparatus shown in FIG. 1 when installed on a roof and connected to an existing vent pipe

[0033]FIG. 7 is a representational view illustrating an old roof, a new roof, insulation therebetween, and an existing roof vent pipe that is too short to extend beyond the elevation of the new roof.

[0034]FIGS. 8a to 8 g illustrate a progression of steps using the apparatus shown in FIG. 1 to extend the roof vent pipe shown in FIG. 7.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0035] As best seen in FIGS. 1 to 5, the vent pipe extension apparatus shown in the drawings comprises an extension pipe coupling generally designated 10, a tubular, generally cylindrical extension pipe generally designated 20, a flashing generally designated 30 and a vent cap generally designated 40. Such apparatus can be used to resolve the problem as described above in relation to FIG. 7 by following the steps indicated in FIGS. 8a to 8 g.

[0036] It should be noted that the combination of coupling 10 and extension pipe 20 itself may be regarded as an extension pipe. This combination is sometimes referred to herein as composite extension pipe 60 or composite pipe 60.

[0037] Also, with reference to FIG. 6 which shows the apparatus of FIG. 1 when installed on roof 200 and connected to vent pipe 150, it should be noted that for clarity of illustration section lines are not shown in the case of coupling 10, flashing 30 and cap 40. Appropriate section lines for these components are shown in FIGS. 2, 4 and 5.

[0038] Referring now to FIGS. 1 to 6, coupling 10 includes cylindrical lower and upper ends 11, 12. Extension pipe 20 includes a lower reduced diameter portion 21 and an elongated tubular portion 22. As best seen in FIG. 6, the inside diameter d3 of extension pipe 20 is greater than the inside diameter d1 of vent pipe 150.

[0039] Lower end 11 of coupling 10 has an outside diameter sized to fit snugly within the inside diameter of vent pipe 150. The fit should be sufficiently tight to preclude the escape of any gases except into extension pipe 20 under worst case pressure conditions that are apt to develop in vent pipe 150. To avoid or minimize the choking of gases exhausting through pipe 150, coupling 10 preferably has a thin wall construction (e.g. 0.050″) such that its inside diameter d2 is only very slightly less than inside diameter d1 of pipe 150. Further, to minimize the likelihood that gases will escape, and although a strong press fit may avoid the necessity, it generally is considered preferable to use a caulking or plumbing sealant (e.g. silicone) between coupling 10 and pipe 150 as indicated by 16 in FIG. 6. As well, to avoid vertical separation between coupling 10 and pipe 150, it generally is considered preferable to secure these component together by suitable fasteners such as fasteners 15 indicated in FIG. 6.

[0040] Upper end 12 of coupling 10 has an inside diameter sized to snugly receive lower end 21 of extension pipe 20. Once again, the fit should be sufficiently tight to preclude the escape of gases except into extension pipe 20. A suitable coupling may be fabricated from various metals (e.g. aluminum, copper).

[0041] Extension pipe 20 may be readily fabricated from off-the-shelf standard size pipe. For example, ABS plastic pipes having standard outside diameters sizes ranging from about 1¼″ to about 12″ and wall thicknesses ranging from about {fraction (1/16)}″ to about ½″ are commonly used for vent pipes for buildings. Reduced diameter portion 21 can be quickly and easily formed using a lathe.

[0042] It will be understood by those skilled in the art that coupling 10 and extension pipe 20 could be fabricated as one integral piece. However, at the present time, it is considered more cost effective to custom fabricate coupling 10 and then to join it with an off-the-shelf pipe in the manner described above.

[0043] Flashing 30 comprises a thin sheet circular base 31 and a centrally positioned cylindrical or tubular portion 32 extending upwardly from the base to a top rim 35. The inside diameter d5 (see FIG. 4) of tubular portion 32 is sized such that the flashing fits as a sleeve over the outside diameter of extension pipe 20. A centrally aligned cylindrical opening 33 having a diameter corresponding to the inside diameter of tubular portion 32 extends lengthwise through base 31 thus permitting flashing 30 to be lowered down over extension pipe 20.

[0044] Flashing 30 may be readily fabricated from thin sheet metal and thin walled metal tubing (e.g. aluminum, copper); tubular portion 32 being welded around its lower perimeter to base 31. As indicated in FIGS. 6, 8e and 8 f, flashing 30 is adapted to be attached to roof 200 by means of conventional fasteners 37.

[0045] As best seen in FIG. 5, vent cap 40 includes a cylindrical inner wall 41 and a cylindrical outer wall 43 with an annular region 45 defined therebetween. Annular region 45 is closed around its top by top 46 and open at its bottom 47. A centrally aligned opening 48 defined by inner wall 41 extends lengthwise through cap 40 to allow the venting gases to external atmosphere. Lower end 42 of inner wall 41 has a slight inward flair. Likewise, lower end 44 of outer wall 43 has a slight outward flair.

[0046] Annular region 45 is sized to telescopically receive the combined wall thickness of tubular portion 22 of extension pipe 20 and tubular portion 32 of flashing 30. A corollary is that inner wall 41 of cap 40 has an outside diameter sized to slidingly fit within the inside diameter of extension pipe 20, and that outer wall 42 has an inside diameter sized to sliding receive the outside diameter of tubular portion 32 of flashing 30. The inward and outward flairs of lower ends 42, 44 of walls 41, 43 provide some initial play that assists to guide cap 40 when being installed to the position shown in FIG. 6 (see also FIGS. 8f, 8 g).

[0047] When installed, vent cap 40 will allow rain or other external precipitation to enter a building's vent pipe system through opening 48. However, such precipitation is anticipated and a building's roof vent pipe system typically will interconnect with a suitable building pipe drainage system. Concurrently, top 46 of vent cap 40 shields the preferably tight annular space between extension pipe 20 and flashing 30 from the rain.

[0048] Vent cap 40 is adapted not only to shield rain from entering the annular space between extension pipe 20 and flashing 30 but, in combination with the radial sizing of extension pipe 20, to discourage or obstruct the movement of venting gases upwardly in the preferably tight annular space between inner wall 41 and extension pipe 20 then downwardly in the annular space between extension pipe 20 and flashing 30. The obstruction of venting gases from moving in this undesirable path is enhanced because the inside diameters d3, d4 (see FIG. 6 of extension pipe 20 and wall 41 are greater than the inside diameter d1 of vent pipe 150. When gases are venting, the region within extension pipe 20 consequently will be a region of reduced pressure compared to the pressure within vent pipe 150, and there will be no undue choking effect at the outlet provided by opening 48 of cap 40.

[0049] It may be observed that if diameter d4 is less than diameter d1 then a tangible threat of choking may arise. Accordingly, diameter d4 should not be less than diameter d1 or, if it is, not by a material amount. Preferably, as is characteristic of the embodiment shown in the drawings, diameter d4 is greater than diameter d1. When extending an existing vent pipe such as vent pipe 150, this avoids the need for any complex engineering analysis of gas flows, temperatures and pressures under anticipated (but perhaps unknown or uncertain) conditions of operation to determine how much if any constriction can be tolerated, and where the choking threshold might lie.

[0050] The use of the apparatus shown in FIG. 1 will now be described with reference to FIGS. 8a to 8 g.

[0051] The first step is to join coupling 10 with extension pipe 20 as indicated in FIG. 8a to form composite extension pipe 60 as shown in FIG. 8b. Composite pipe 60 is then coupled with vent pipe 150 as shown in FIG. 8c. Although not shown in FIGS. 8a to 8 g, this may (and preferably does) include the use of fasteners 15 and caulking 16 as described above in relation to FIG. 6. At this point, no new roof has been installed over existing roof 100.

[0052] Next, insulation 250 and new roof 200 is added. Then, flashing 30 is lowered down over composite pipe 60 as indicated in FIG. 8d until its rests on upper surface 201 of roof 200 as shown in FIG. 8e. In this position, it will be noted that a top part 25 of composite pipe 60 extends above rim 35 of flashing 30. Also, the flashing is ready to be attached to roof 200 by means of fasteners 37.

[0053] Next, as shown in FIG. 8f, the flashing is fully attached to roof 200 by fasteners 37. Further top part 25 is cut from composite pipe 60 (and discarded) leaving an upper rim 27 flush with rim 35 of flashing 30. Normally (for example when the pipe to be cut is fabricated from ABS plastic) the cut can be made easily and quickly with a suitable saw. Preferably, the flashing is attached to roof 200 beforehand.

[0054] Finally, the extension is capped and sealed with cap 40 in the manner indicated in FIGS. 8f and 8 g (see also FIG. 2). Optionally, when cap 40 is in position as shown in FIGS. 2 and 8g, it may be more firmly secured by fasteners (not shown) extending through its outer wall and flashing 30. However, this merely serves to discourage vandalism. It does not alter or improve the functioning of the cap.

[0055] It will be appreciated by those skilled in the art that many of the details provided above are by way of example only and are not intended to limit the scope of the invention which is to be interpreted with reference to the following claims. 

What is claimed is:
 1. Apparatus for extending the length of a vent pipe for a predetermined distance above the elevation of a building roof, said vent pipe having a known inside diameter, said apparatus comprising: (a) an extension pipe characterized by: (i) a lower end having a cylindrical outside diameter sized to fit snugly within said inside diameter of said vent pipe; and, (ii) an elongated tubular portion extending upwardly from said lower end, said tubular portion having: (A) an inside diameter greater than said inside diameter of said vent pipe; and, (B) an outside diameter, (b) a flashing, said flashing comprising a base attachable to said roof and a centrally positioned tubular portion extending upwardly from said base, said tubular portion characterized by: (i) an inside diameter sized to fit as a sleeve over said extension pipe; and, (ii) an outside diameter; said base including a centrally aligned opening having a diameter corresponding to said inside diameter of said tubular portion and extending lengthwise through said base for permitting said flashing to be lowered as a sleeve over said extension pipe; and, (c) a vent cap comprising an inner wall and an outer wall with an annular space defined between said walls, said annular space having a closed top and an open bottom, said inner wall defining a centrally aligned opening extending lengthwise through said cap, and wherein: (i) said inner wall has an outside diameter sized to slidingly fit within said inside diameter of said extension pipe; (ii) said outer wall has an inside diameter sized to slidingly receive said outside diameter of said tubular portion of said flashing.
 2. Apparatus as defined in claim 1, wherein (a) said tubular portion of said flashing has a tubular wall thickness substantially less than the tubular wall thickness of said upper end of said extension pipe; (b) said inner wall of said vent cap has a wall thickness substantially less than the tubular wall thickness of said upper end of said extension pipe; and, (c) said inner wall of said vent cap has a wall thickness substantially less than the tubular wall thickness of said upper end of said extension pipe.
 3. Apparatus as defined in claim 2, wherein said centrally aligned opening in said vent cap has a bottom diameter not less than said inside diameter of said vent pipe.
 4. Apparatus as defined in claim 2, wherein said centrally aligned opening in said vent cap has a bottom diameter greater than said inside diameter of said vent pipe.
 5. Apparatus as defined in any of the preceding claims, wherein said extension pipe includes a pipe coupling having a lower end and an upper end, the lower end of said coupling forming said lower end of said extension pipe, the upper end of said coupling connecting with said elongated tubular portion of said extension pipe.
 6. Apparatus for extending the length of a vent pipe for a predetermined distance above the elevation of a building roof, said vent pipe having a known inside diameter, said apparatus comprising: (a) an elongated extension pipe connectable with said vent pipe to receive gases flowing upwardly from said vent pipe; (b) a flashing attachable to said roof while fitted as a sleeve over said extension pipe; and, (c) a vent cap fittable over said flashing and said extension pipe to shield the annular region between said flashing and said extension pipe from external precipitation, said vent cap including an opening for venting to external atmosphere gases received by said extension pipe from said vent pipe, said extension pipe and said vent cap being sized so as to maintain a venting pressure in said extension pipe not greater than the venting pressure in said extension pipe.
 7. Apparatus as defined in claim 6 wherein said opening in said vent cap has a bottom diameter not less than said inside diameter of said vent pipe.
 8. Apparatus as defined in claim 6 wherein said opening in said vent cap has a bottom to diameter greater than said inside diameter of said vent pipe.
 9. On a building where a new roof is constructed atop an old roof, and where an existing vent pipe extending above the old roof is of insufficient length in relation to the new roof, a method of extending the length of the existing vent pipe above the elevation of the new roof, said method comprising: (a) connecting an upwardly extending, elongated extension pipe with said vent pipe to receive gases flowing upwardly from said vent pipe, said extension pipe having sufficient length to extend from said vent pipe to a desired distance above said new roof; (b) fitting a flashing as a sleeve over said extension pipe; (c) attaching said flashing to said new roof when so fitted; and, (d) fitting a vent cap over said flashing and said extension pipe to shield the annular region between said flashing and said extension from external precipitation, said vent cap including an opening for venting to external atmosphere gases received by said extension pipe from said vent pipe, said extension pipe and said vent cap being sized so as to maintain a venting pressure in said extension pipe not greater than the venting pressure in said extension pipe.
 10. A method as defined in claim 9, wherein said extension pipe and said vent cap are sized so as to maintain a venting pressure in said extension pipe less than the venting pressure in said extension pipe.
 11. A method as defined in claim 9 wherein said vent pipe and said extension pipe are generally cylindrical, said extension pipe having an inside diameter greater than the inside diameter of said vent pipe.
 12. A method as defined in any of claims 9 to 11, further comprising the step of cutting a top part away from said extension pipe leaving an upper rim of said extension pipe flush with an upper rim of said flashing. 